Avalanche Forecast

Issued: Feb 13th, 2013 9:35AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Wind Slabs, Storm Slabs and Persistent Slabs.

triley, Avalanche Canada

Cariboos.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Thursday

Weather Forecast

Overnight and Thursday: Mostly clear with cold temperatures overnight and nil precipitation. Moderate Westerly winds are expected to decrease to light Northwesterly by morning. Freezing levels down to the valley bottom overnight, and then rising up to about 1100 metres during the day. Some light precipitation may start by evening.Friday: Moderate West winds with Alpine temperatures around -6.0 and freezing levels rising to around 1200 metres. High overcast becoming cloudy with flurries starting in the evening. Saturday: Flurries becoming light snow overnight. Expect 5-10 cms during the day.

Avalanche Summary

Natural avalanches up to size 2.5 were reported from various aspects. Avalanches were reported to be dry slabs, and mostly from steep unskiable terrain.

Snowpack Summary

There is a new soft slab that is 20-40 cms thick that is sitting on a new layer of surface hoar that was buried on February 12th. This soft slab is expected to be reactive to light additional loads and may result in avalanches up to size 2.0. Before this new slab developed, there were various surfaces that consisted of wind slab in exposed lee alpine terrain, sun crust on solar aspects, and surface hoar or facets on shady slopes. Below this up to 40 cm of settled storm snow sits on old wind slabs and recently buried weak layers. The late January surface hoar, sun crust, and/or facet layer is down around 80 cm deep and remains a concern for triggering. Use extra caution on large open slopes, cutblocks and convex rolls at and below treeline where the buried surface hoar may be preserved.Cornices are reported to be large throughout the region. The mid-pack is generally well settled and strong and the average snowpack depth at treeline elevations is near 200 cm.

Problems

Wind Slabs

Wind slabs continue to be a concern on lee slopes and behind terrain features like ridges and ribs. They could be triggered under the weight of a person. Looming cornices may threaten slopes below.

Avoid freshly wind loaded features.>Be cautious as you transition into wind affected terrain.>

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Storm Slabs

A new soft storm slab has developed above surface hoar and sun crusts that developed during the recent clear weather. The new storm slab is between 20-40 cms deep and reported to be easy to trigger by skiers or snowmobilers (riders).

Plan escape routes and identify safe zones before committing to your line.>Ride slopes one at a time and spot for your partners from safe locations.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

A persistent weak layer of surface hoar, crusts and/or facets lurks around 80 cm deep. This weakness may be reactive to human triggers and can be difficult to predict.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Feb 14th, 2013 2:00PM